I'm curious. Could you elaborate on which types of tunes work better on fretted to justify the switch?
Certainly. First off, my current band plays pop and rock songs, not jazz. Secondly, we don't have a guitar player, so on some songs I play guitar-like arrangements. For example, the intro to Adele's 'Rolling in the Deep' has a crunchy muted chugging 1/8th notes, and the intros to Cyndi Lauper's 'Time After Time' and 'Don't Speak' from No Doubt have a fingerpicked legato argeggii and double-stops in the upper octave that need the brightness of frets and rounds.
I take high-range solos in 'It's Too Late' from Carole King and 'Smooth Operator' by Sade, and although either can be played fretless - intonation in that register is not a problem - I think the solos works much better with a bit of fret grind, a glassy top end and a layer of chorus. Other tunes that work better include 'The Logical Song' by Supertramp and 'Just The Two Of Us' by Grover Washington, which really needs the slap tone in the chorus. 'Piece of my Heart' from Erma Franklin sounds much better with a fretted bass and vintage Bassman or B15 amp sim. 'Go Your Own Way' from Fleetwood Mac and the Pretenders' songs 'Talk of the Town' and 'Brass In Pocket' all come to life with the combination of clank and thump that only a fret can provide.
Fretless essentials include Allannah Miles' 'Black Velvet', 'Circle In The Sand' by Belinda Carlisle, 'Chains' by Tina Arena, 'Songbird' by Fleetwood Mac, 'It's Alright (Baby's 'Coming Back)' from Eurythmics, 'Walking On Broken Glass' by Annie Lennox, 'All Cried Out' from Alison Moyet, 'Set Fire to the Rain' from Adele, 'Rather Be' by Jess Glynne/Clean Bandit, 'Spotlight' from Jennifer Hudson (two versions), 'Stop!' from Sam Brown, 'The Man With the Child in his Eyes' by Kate Bush, 'Valentine Blues' by Jools Holland and 'Will You' from Hazell O'Connor, where I play the sax solo on fretless bass. 'Feel Like Making Love', 'Wish I Didn't Miss You' and 'Constant Craving' also get the fretless treatment. There are others, but I think you probably see where I am coming from.